Interactions of CF1, the coupling factor of photophosphorylations with chloroplast lipids. Monolayers studies

Surface pressure and surface potential of monolayers at a water–air interface show no polar interactions between the chloroplast total lipids and the polar protein CF1. The two components are perfectly miscible in mixed monolayers. It follows that CF1 interacts with the hydrophobic parts of the lipid molecules and that, in vivo, CF1 could penetrate in the hydrophobic core of the membranes

The 6-Kilobase C-Erbb2 Promoter Contains Positive and Negative Regulatory Elements Functional in Human Mammary Cell Lines

peer reviewedA 6-kilobase fragment extending at the 5'-end of the c-erbB2 protooncogene was isolated from a normal human lymphocyte genomic DNA library. The full-length fragment and five subfragments with identical 3'-ends were obtained by progressive unidirectional deletion from the 5'-end and were cloned in front of the luciferase reporter gene. The hybrid genes were analyzed for transcriptional activity in human mammary cell lines synthesizing low (HBL-100 and T-47D), moderate (MDA-MB-453), or high (BT-474) amounts of the c-erbB2 mRNA and were also analyzed in HeLa cells. Gene-specific expression was observed, indicating the presence of multiple cis-acting sequences in the c-erbB2 promoter. A major negative element is located in the -2- to -4-kilobase region. It is flanked on both sides by positive elements that display enhanced transcriptional activity in the BT-474 tumor cells only. While predominant in the low-expressing cells, the effect of the repressor appears to be overcome by the distal transactivator in the high-expressing BT-474 cells, resulting in a 15 to 50 times increase in luciferase activity relative to the HBL-100 and T-47D cells, respectively. Cell-specific expression relies on the trans-acting factors present in the different cell lines. The formation of cell-specific protein-DNA complexes was demonstrated by gel retardation assay

The 6 kb c-erbB2 promoter contains positive and negative regulatory elements functional in human mammary cell lines.

peer reviewedA 6-kilobase fragment extending at the 5'-end of the c-erbB2 protooncogene was isolated from a normal human lymphocyte genomic DNA library. The full-length fragment and five subfragments with identical 3'-ends were obtained by progressive unidirectional deletion from the 5'-end and were cloned in front of the luciferase reporter gene. The hybrid genes were analyzed for transcriptional activity in human mammary cell lines synthesizing low (HBL-100 and T-47D), moderate (MDA-MB-453), or high (BT-474) amounts of the c-erbB2 mRNA and were also analyzed in HeLa cells. Gene-specific expression was observed, indicating the presence of multiple cis-acting sequences in the c-erbB2 promoter. A major negative element is located in the -2- to -4-kilobase region. It is flanked on both sides by positive elements that display enhanced transcriptional activity in the BT-474 tumor cells only. While predominant in the low-expressing cells, the effect of the repressor appears to be overcome by the distal transactivator in the high-expressing BT-474 cells, resulting in a 15 to 50 times increase in luciferase activity relative to the HBL-100 and T-47D cells, respectively. Cell-specific expression relies on the trans-acting factors present in the different cell lines. The formation of cell-specific protein-DNA complexes was demonstrated by gel retardation assay